The present invention relates to an apparatus for the precision measurement of the optical characteristics of the eye and the shape of the cornea and, more particularly, to an optical characteristic measuring apparatus capable of measuring optical characteristics of an irregular astigmatism component.
A conventional optical characteristic measuring apparatus for measuring the optical characteristics of the eye known as a refractometer is capable of expressing the optical characteristics of the eye merely as a spherical component, a regular astigmatism component and the angle of the axis of the regular astigmatism component.
Some eyes have an irregular astigmatism component in addition to a regular astigmatism component. Irregular astigmatism cannot be corrected by a pair of spectacles if the quantity of the irregular as astigmatism component is large, contact lens most be used instead of a pair of spectacles lens, the eye must be examined by a medical doctor.
However, the conventional optical characteristic measuring apparatus for measuring the optical characteristics of the eye, such as a refractometer, is used only for reforming a pair of spectacles and its performance is not fully satisfactory. Accordingly, desired eagerly was an appearance of an optical characteristic measuring apparatus capable for accurately measuring the irregular astigmatism component of the eye in addition to the spherical component, the regular astigmatism component and the angle of the axis of the regular astigmatism component.